Automobiles, truck, trailers, and other vehicles are required by law to have approved lighting devices. Such lighting devices provide illumination, indicate a vehicle's presence and width, indicate braking, and inform others when a vehicle is turning or about to change lanes. To such ends both Federal and State laws mandate the color, location, number, height above ground, illumination intensity and other aspect of vehicle lighting.
If a vehicle's lighting is substandard, such as having a bulb, fuse, or switch out a driver can be ticketed for operating an unsafe vehicle. While nobody likes getting a ticket for non-working vehicles lights the reasons for enforcement are obvious. Furthermore, operating a vehicle with substandard lighting is dangerous and an all too-common source of accidents.
Determining the proper operation of headlights is simple: they either work and you can observe their illumination or they do not work and you can determine from the lack of illumination that they are not working. However, determining the proper operation of a vehicle's tail lights is far more difficult. One (1) way of doing so is to leave the vehicle, have another person operate the lights, turn signals, and brakes, and directly observe the proper operation. While extremely effect, that method is only applicable to stationary vehicles. It is also possible to use a second vehicle that follows the first to determine if the first vehicle's lighting is operating properly. This requires two (2) vehicles, two (2) drivers, and a coordinated, pre-planned activity it is not particularly practical.
Therefore, devices for allowing drivers to determine the proper operation of their vehicle's tail lighting would be useful. Particularly beneficial would be low cost devices that enable drivers to determine the proper operation of their vehicle's tail lighting. Preferably such devices would be easy to use and useful with existing rear vehicle lighting systems.